Garlic is one of those ingredients that can can instantly spark a debate. Some people swear by its traditional uses, others believe it should never be given to a dog or cat.
So, what's the truth?
We're diving deep into myths, the facts, the potential benefits and risks, and how it gained such a bad reputation amongst animal-lovers.
Why Is Garlic Considered Toxic to Dogs?
Garlic (Allium sativum) belongs to the Allium family, alongside onions, leeks and chives. These plants contain compounds that can cause oxidative damage to red blood cells in susceptible animals.
Red blood cells carry oxygen around the body. When these cells become damaged, they can break down prematurely, potentially leading to a condition called haemolytic anaemia.
So while garlic contains natural compounds that researchers have studied for their antimicrobial and antioxidant properties, it can also damage red blood cells in animals when they consume high doses of it.
The key words being 'high doses'.
Seems reasonable, but why is everyone so scared? That comes down to a few studies in particular.
The Garlic Study That Fuelled the Fear
An often referred to study was published by Lee and colleagues in 2000 in the American Journal of Veterinary Research. The researchers studied eight healthy adult dogs. Four of them received garlic. The other four received water as a control.
The four dogs who were on the garlic, received a garlic extract equivalent to 5g of whole garlic per kilogram of body weight. It was administered directly into the stomach once a day for seven days.
To put that into perspective: for a 20 kg dog, the dose was equivalent to 100 g of whole garlic per day — roughly 15–20 average-sized garlic cloves' worth.
So we're talking about an excessive amount, administered repeatedly over a short period.
The researchers found changes in the dogs' red blood cells, including decreases in red blood cell count, haematocrit and haemoglobin. They also observed Heinz bodies and eccentrocytes, which are markers of oxidative damage to red blood cells.
However, none of the dogs developed clinical haemolytic anaemia during the study. The researchers observed temporary changes in the red blood cells, which resolved naturally without treatment during the 30-day observation period.
But it was enough for the fear to take hold.
The findings in this first study do matter because they show that garlic can damage red blood cells in dogs at high doses. However, that study involved only eight dogs and examined a specific, extremely high-dose exposure over seven days, rather than a lower or even moerate dose.
What about the 2018 garlic study?
A later study explored a different preparation of garlic over a much longer period.
In 2018, researchers gave beagles aged garlic extract (AGE) at doses of 45 or 90 mg/kg daily for 12 weeks. They found no evidence of red blood cell damage in the dogs and reported no significant adverse effects at the higher dose.
The researchers also observed changes in the expression of genes involved in the body's antioxidant defence pathways.
This is an important distinction: the study examined aged garlic extract, not fresh garlic. The ageing and extraction process changes garlic's chemical composition, so we can't directly compare the doses used in these two studies.
Together, the studies show why it's worth looking at the specific preparation, dose and research findings rather than treating every form of garlic as identical.
Read the original studies:
-
Lee et al. (2000) — Garlic extract and red blood cell changes in dogs
-
Yamato et al. (2018) — Safety and efficacy of aged garlic extract in dogs
Does garlic deter fleas and ticks?
Garlic has a long history of traditional use, including in natural approaches to animal care.
In appropriate doses, garlic provides sulphur compounds and aromatic constituents that make for an unappealing environment to pests.
If you're looking for ways to support your pet naturally, we have a range of garlic products that can be used to support natural care.
Fleedom https://greenpet.com.au/products/greenpet-fleedom-food-supplement
Garlic Granules https://greenpet.com.au/products/garlic
Garlic Powder https://greenpet.com.au/products/garlic-powder
The Bottom Line
Like many natural ingredients, garlic deserves a closer look rather than a blanket label of 'dangerous'. The form of garlic and the amount used both matter. Garlic also contains compounds with antioxidant properties and has a long history of medicinal use.
Natural ingredients deserve the same thoughtful evaluation as any other substance we give our animals, and understanding the context and benefits, not just the risks, helps us make more informed choices about animal health.
References and Further Reading
Lee, K. W. et al. (2000). Hematologic changes associated with the appearance of eccentrocytes after intragastric administration of garlic extract to dogs. American Journal of Veterinary Research, 61(11), 1446–1450. https://pubmed.ncbi.nlm.nih.gov/11108195/
For another look at the research behind garlic and its use in dogs, check out this article from Dr Karen Becker.
https://www.proactivepaws.com/blogs/pet-health/garlic-for-dogs-safe-or-toxic?